class_docstr: A tool to enforce non-reentrancy.
  Mostly used on DataFlow whose :meth:`get_data` is stateful,
  so that multiple instances of the iterator cannot co-exist.
code: def __exit__(self, exc_type, exc_val, exc_tb):
      self._lock.release()
      return False
  
imports: import threading
  from abc import ABCMeta, abstractmethod
  import six
  from ..utils.utils import get_rng
label_desc: Use image node_id 3 for calling the DataFlowReentrantGuard obj's underlying member method code with example usage: obj.__exit__(exc_type, exc_val, exc_tb) and returns: False